g0201_0300.s0297_serialize_and_deserialize_binary_tree.Codec.kt Maven / Gradle / Ivy

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Kotlin-based LeetCode algorithm problem solutions, regularly updated

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package g0201_0300.s0297_serialize_and_deserialize_binary_tree

// #Hard #Top_Interview_Questions #String #Depth_First_Search #Breadth_First_Search #Tree
// #Binary_Tree #Design #Data_Structure_II_Day_18_Tree #Udemy_Tree_Stack_Queue
// #2022_11_06_Time_475_ms_(78.85%)_Space_50.3_MB_(64.42%)

import com_github_leetcode.TreeNode

/*
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */

class Codec {
    private var offset = 0

    // Encodes a tree to a single string.
    fun serialize(root: TreeNode?): String {
        val sb = StringBuilder()
        offset = 0
        serialize(root, sb)
        return sb.toString()
    }

    fun serialize(root: TreeNode?, sb: StringBuilder) {
        // all nodes fit into 4 bits.
        // IFF we offset at 0. So encode(val) = val + min(default - 1000)
        if (root == null) {
            sb.append(DELIM)
            return
        }
        val s = Integer.toHexString(root.`val` + BASE_OFFSET)
        val sb2 = StringBuilder()
        for (i in 0 until 3 - s.length) {
            sb2.append('0')
        }
        sb2.append(s)
        sb.append(sb2)
        serialize(root.left, sb)
        serialize(root.right, sb)
    }

    // Decodes your encoded data to tree.
    fun deserialize(data: String): TreeNode? {
        if (data[offset] == '*') {
            offset++
            return null
        }
        val root = TreeNode(
            data.substring(offset, offset + 3).toInt(16) - BASE_OFFSET
        )
        offset += 3
        root.left = deserialize(data)
        root.right = deserialize(data)
        return root
    }

    companion object {
        private const val BASE_OFFSET = 1000
        private const val DELIM = "*"
    }
}

/*
 * Your Codec object will be instantiated and called as such:
 * var ser = Codec()
 * var deser = Codec()
 * var data = ser.serialize(longUrl)
 * var ans = deser.deserialize(data)
 */